The present invention relates to a molding apparatus and method for containers, and particularly to such apparatus and method in which between a heating section and a blow molding section, the temperature of preforms is conditioned in a standby section.
Methods for blow molding a container from a cylindrical preform (parison) include that known as the cold parison or 2-stage method and that known as the hot parison or 1-stage method. In the cold parison method (2-stage method), a preform at room temperature must be heated to at least the temperature at which blow molding becomes possible, or the so-called blow molding temperature, and in the hot parison method (1-stage method), heating is not required for as long as in the cold parison method, but it is still necessary to heat to at least the blow molding temperature since the preform retains the heat from the injection molding stage.
In both of these methods, the heating to the blow molding temperature is carried out uniformly around the circumferential direction of the preform.
On the other hand, when blow molding containers of special shape, such flat containers, if a preform is used with just the above described heating, this produces portions of the container with thick walls and other portions with thin walls since there are portions which are stretched greatly and portions which are stretched much less.
To avoid this situation, it is necessary to apply a temperature distribution to the preform, so that the portions which are stretched more are at a lower temperature than other portions. To apply such a temperature distribution, partial temperature conditioning must be applied to the preform.
However, adding the temperature conditioning apparatus to implement such partial temperature conditioning of the preforms makes the molding apparatus large, and not only is it not possible to save space, but also the cost is increased.